1. Field of the Invention
The present invention relates to a work transfer method and a work transfer apparatus in a machine tool with a movable main spindle (i.e., movable spindle type machine tool) and a machining system therefor. In this machine tool, a headstock for rotatably supporting the spindle may move at least in an axial direction (Z-axis direction) of the spindle and in a direction (X-axis direction) perpendicular to the axial direction of the spindle. The work transfer apparatus serves to transfer a work (workpiece) in and out. The machine tool receives and sends the work between a chuck provided at a lower end of the spindle and the apparatus for transferring the work.
2. Related Art
A work changer for changing works for the machine tool with the movable main spindle as related art (Japanese Patent Application No. 9-362060, i.e., Japanese Patent Application Laid-Open No. 11-170101) has been proposed. In this work changer, two or four portions for placing the works are formed in parallel with each other in a horizontal plane, and these portions for placing the works (work placement portions) are rotated or moved back and forth.
Also, other related arts such as a work feeder in the machine tool with the movable main spindle (Japanese Patent Application No. 9-297774, i.e., Japanese Patent Application Laid-Open No. 11-114701) and a work stocker (Japanese Patent Application No. 10-48840, i.e., Japanese Patent Application Laid-Open No. 11-226801) have been proposed. In the work feeder and the work stocker, a plurality of portions for placing the works are rotated in a horizontal plane to thereby feed the work to the machine tool or remove it from the machine tool.
In any piece of the above-described related art, the plurality of work placement portions on which the works are to be laid are not arranged in the two stages in the vertical direction but in the horizontal plane. As a result, an apparatus for moving the work placement portions tends to be enlarged. In particular, in the case where the works having a large diameter are to be transferred, the work placement portions become large in physical size.
Also, a headstock of the machine tool moves in the X-axis direction to perform the operation to receive a work which has not been machined, after a work that has been machined is laid on the work placement portion within a work receiving/sending region. When the headstock performs the receiving/sending operation of the work, the distance of movement in the X-axis direction of the headstock tends to be elongated.
Thus, not only may an apparatus for transferring the work itself be enlarged but also it is necessary that the headstock be moved in the X-axis direction to perform the work receiving/sending operations, accordingly, this leads to an enlargement of the machine tool as a whole.
As a result, it is difficult to use in common the machine tool for machining the work having a large diameter and the machine tool for machining a standard size work. Also, as a result of the enlargement of the work transfer apparatus and the operation of movement of the headstock, it tends to take long time for changing the works.